docs: def canonify(self):
          """
          Transform self to an equivalent canonical form:
          delete optdict keys with False value, move optdict keys
          with True value to optlist, stringify other values.
          """
  
          for k, v in self.optdict.items():
              if v == False:
                  self.optdict.pop(k)
              elif v == True:
                  self.optdict.pop(k)
                  self.optlist.add(v)
              else:
                  self.optdict[k] = str(v)